1. Field of the Invention
The present invention relates to a rubber patch for repairing both tubeless and tube-type tires, with a radial-ply structure, in which three or more of the metallic cords in their sidewalls have been strained or broken. The rubber patches can be applied both to tires which need repairing and to one which require retreading.
2. The Prior Art
The previous trapezoidally-shaped rubber patches, invented by the same applicant, were intended to replace the traditional rectangular patches. These consisted of several superimposed layers of fabric made of synthetic fibers and metallic cords and have indeed most successfully resolved the problem of repairing and retreading radial-ply tires with damaged sidewalls. However, it was realized that these new rubber patches needed further improving to eliminate the problems arising from their application, problems which are listed below:
(1) The impossibility of placing the rubber patches with their metallic cords exactly parallel to and overlying the still good parts of the metallic cords of the tire which need repairing. This is because it is impossible to find the areas in the rubber patches where these cords have been inserted. Consequently, for this operation to be done to perfection it takes a long time.
(2) During vulcanization of the rubber patches to the tire, the former may be shifted by the thrusting pressure of the upper part of the mold on the rubber patch itself, especially at the edges of rubber patch beneath the rubber plug; after vulcanization and inflating for use, this may cause localized bulges in the tire because the cords of the plug and the ones in the tire are not perfectly parallel.
(3) The need, in order to apply the patches, to remove the inside layers of rubber covering the radial cords of the tire for all the area of the patch. This is because the attachment surface of the rubber patch itself, including the layer of rubber with metallic cords, is completely flat and, therefore, it is necessary to create a cavity with a surface area equal to that of the whole rubber patch if the metallic cords of the patch are to directly touch those of the tire.
Furthermore, during the manufacture of the rubber patch, slight distortions occur in the layer of rubber with metallic cords, in the layers of butyl rubber, and in the rubber fabrics during molding and vulcanization.